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| Paper: |
Precise Radial-Velocity Measurements with a Cassegrain Spectrograph, I: Wavelength Calibration |
| Volume: |
185, Precise Stellar Radial Velocities, IAU Colloquium 170 |
| Page: |
63 |
| Authors: |
Ilyin, I. V.; Duemmler, R. |
| Abstract: |
Radial velocity measurements using the cross-correlation method are discussed and the accuracy of the relative offset determination is derived. The wavelength stability of a high resolution echelle spectrograph mounted at the Cassegrain focus is analysed. A new method is developed, which allows to correct for the change of the positions of the comparison spectrum lines during the scientific exposure by means of a three-dimensional dispersion curve. The 3D-curve is a composition of the individual dispersion curves of several images, where also the effects of the misalignment of the spectral lines with respect to the CCD rows, and optical distortion in the spectrograph are taken into account and considered as a function of time as the spatial orientations of the telescope and the spectrograph change. The method is used to investigate the instability of the radial velocities of some late-type giants, based on observations with the high resolution echelle spectrograph Sofin, mounted at the Cassegrain focus of the Nordic Optical Telescope, La Palma, Canary Islands. |
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